Automatic switch for telephone systems



March 23, 1954 P. BAKKER AUTOMATIC SWITCH FOR TELEPHONE SYSTEMS Filed Aug. 25, 1950 2 Sheets-Sheet l INVENTOR Pier Bakker BY @"e" @A ys.

March 23, 1954 P. BAKKER AUTOMATIC SWITCH FOR TELEPHONE SYSTEMS 2 Sheets-Sheet 2 Filed Aug. 25,4 1950 INVENTOR. P/'er Bakker BY ,n 4%@ M Afys.

Patented Mar. 23, 1954 UNITED STATES AUTOMATIC SWITCH FOR TELEPHONE SYSTEMS Pier Bakker, Chicago, Ill., assigner to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application August 25, 1950, Serial No. 181,510

Claims.

The present invention relates to telephone systems, and more particularly to automatic switches for use in toll switching telephone systems.

It is a general object of the present invention to provide in a toll switching telephone system an improved and simplified automatic switch.

Another object of the invention is to provide a combination one-digit and two-digit automatic switch that includes a pair of wiper sets and embodies an improved and simplied wiper switching arrangement.

Another object of the invention is to provide a selector switch that embodies an improved impulsing and supervisory relay network.

A further object of the invention is to provide a combination selector switch and repeater of the improved character noted.

Further features of the invention pertain to the particular arrangement of the circuit elements of the automatic switches, whereby the above-outlined and additional operating features thereof are attained,

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which Figure 1 is a circuit diagram of a combination one-digit and two-digit selector switch emodying the present invention; and Fig. 2 is a circuit diagram of a combination one-digit and two-digit selector switch-repeater embodying the present invention.

Referring now more particularly to Fig. l, the toll selector I0!) there illustrated, and embodying the features of the present invention, is of the combination one-digit and two-digit type. The selector III!! comprises a Strowger mechanism I9@ including a lower wiper set ISI and an upper wiper set E92, as well as lower and upper contact banks respectively accessible to the two wiper sets noted; each of the contact banks comprises a plurality and maximum of ten vertically spaced-apart levels or rows of individual contact sets disposed in spaced relation in the rotary direction; and certain of the levels of contact sets in the respective lower and upper contact banks are paired so that the respective lower and upper wiper sets ISI and |92 have simultaneous access thereto.

Further, the toll selector I occupies an intermediate position in a toll switch train, and further includes an incoming trunk I 0I that is accessible to preceding toll switching apparatus, not shown, that is, in turn, accessible to a toll operator switchboard, not shown. Also the contact sets provided in the various levels of the lower and upper .contact banks terminate groups of trunks extending to succeeding toll switching appara- 2 tus, not shown. The portions of the toll switch train preceding and succeeding the toll selector it have not been illustrated in the interest of brevity.

Specifically, in the contact banks of the Strowger mechanism Ist, the lower wiper set I9I has access to a level of contact sets terminating a group of outgoing trunks H12, etc., and the upper wiper set ISE has access to a level of contact sets terminating a group of outgoing trunks |03, etc., these levels in th respective lower and upper wiper sets I 9| and I 92 have simultaneously access to the outgoing trunks ISZ and |03. Also the lower contact bank of the Strowger mechanism IQ comprises a level of contact sets terminating a group of outgoing trunks IM, etc.. accessible to the lower wiper set ISI. In the toll selector IGI), the incoming trunk I DI comprises a pair of line conductors, a hold conductor, and a control conductor respectively marked -I-, |52, etc., comprises a pair of line conductors, a hold conductor and a control conductor.

Further the Strowger mechanism comprises a vertical magnet MI 93 for driving the wiper carriage, mounting the lower and upper wiper sets I SI and E92, step-by-step in the vertical direction away from its normal vertical position, a rotary magnet MI94 wiper carriage step-by-step in rection away from its normal rotary position, and a release magnet MISS for releasing the wiper carriage and for causing it to be returned to its normal rotary and vertical positions. Also associated with the wiper carriage of the Strowger mechanism ISD are two sets of switch springs SI23 and Si24 that are operated when the wiper carriage is moved one step in the vertical direction away from its normal vertical position, and three sets of switch springs SI25, SIZE and SI 21 that are operated when the wiper carriage is moved eleven steps in the rotary direction away from its normal rotary position. Finally a set of switch springs SI28 is associated with the wiper carriage of the Strowger mechanism |90 that is operated when the wiper carriage is moved in the vertical direction a predetermined number of steps corresponding to the level of the group of trunks IM, etc., appearing before the lower wiper set I9I.

Finally the toll selector Il!!! comprises a relay through relay RIII), a line relay RI20, a hold relay RI30, a transfer RISII, a count relay switching relay RI80.

First assuming that a connection is to be extended via the toll switch train by Way of the toll selector |00 and by way of one of the out,-

lector 10S via the incoming trunk 101, ground potential is applied to the hold conductor of the incoming trunk 101 and a loop circuit is completed between the line conductors of the incoming trunk 101 so as to energize in series the upper and lower windings of the line relay R120 in order to cause the latter relay to operate. This loop circuit also includes the contacts 112 and 115. Upon. operating, the line relay R20 completes, at the contacts 121, a circuit, including the contacts 119, for operating the hold relay R130. Upon operating, the hold relay R130 completes, at the contacts 13|, a path for applying ground potential to the hold conductor of the incoming trunk 151 in order further to hold the preceding toll switch train and to mark as busy thereto the incoming trunk i01. Also the hold relay R135 completes, at the contacts 135, a circuit, including t'ne set of switch springs S124, for energizing the lower winding of the transfer relay Ritt in order to cause the latter relay to operate.

At this time, the iirst digit is received over the line conductors of the incoming trunk 101 in 0rder to cause the line relay Riz to follow; and it may be assumed that this iirst digit is the digit l. Accordingly, the line relay R120 restores and then reoperates, interrupting and then recompleting, at the contacts 121, the circuit for energizing the winding of the hold relay R130 in order to cause the latter relay to remain operated during impulsing as it is of the slow-torelease type. Also the line relay R20 completes and then interrupts, at the contacts 122, a circuit, including the contacts 119, 133 and M5, for energizing the upper winding of the transfer relay RM1) in multiple with the vertical magnet M103 so as to retain the transfer relay R140 in its operated position during impulsing as it is of the slow-to-release type and to effect operation and restoration of the vertical magnet M193 so that the wiper carriage of the Strowger mechanisrn 1&0 is driven one step in the vertical direction away from its normal vertical position. When the wiper carriage of the Strowger mechanism 1&50 is thus driven one step away from its normal vertical position, the sets of switch springs S123 and S125 are operated. Specifically, the set of switch springs S123 is closed to prepare la circuit traced hereinafter for operating the release magnet M196 of the Strowger mechanism 190; and the set of switch springs S125 is opened to interrupt the previously-traced circuit for energizing the lower winding of the transfer relay R140. Also when the wiper carriage of the Strowger mechanism 1% is driven one step in theY vertical direction away from its normal vertical position, the lower and upper wiper sets 151 and 192 are moved together so that they respectively select the two groups of outgoing trunks respectively including the outgoing trunks 1112 and 103. In passing, it is noted that the count relay R150 normally occupies its restored position so that the lower wiper set 191 is normally effectively selected, at the contacts 132,104,136 and 138.

At the conclusion of the first digit l, the line relay R120 is retained in its operated position in order to retain operated the hold relay R13 so that the transfer relay R140 restores shortly thereafter, the latter relay being of the slow-tcrelease type. Upon restoring, the transfer relay R140 interrupts, at the contacts 145, a further point in the circuit for operating the vertical magnet Mi93, and prepares, at the contacts 144, a point in a circuit traced hereinafter for energizing the winding of the rotary relay R150.

W hen the second digit is received, the line relay R again follows; and in the present instance, the second digit is the line relay R120 restores and then reoperates retaining operated the hold relay R during impulsing as it is of the slow-to-release type. Also the line relay R120 upon restoring completes, at the contacts 122, the previously-mentioned circuit, including the contacts 110, 133, 1M and 12 for energizing the winding of the rotary relay R55, as well as a multiple circuit, including the contacts 163, for energizing the upper winding of the count relay R160. The rotary relay R opcrates to complete, at the contacts 153, an alternative path in the circuit for energizing the winding thereof; while the count relay R operates only through its rst step; this relay 'being of the two-step type. Upon operating through its first step, the count relay R160 closes only the contacts 165, completing a path, including the contacts 135, for short-circuiting the lower winding thereof. The path for short-circuiting the lower winding of the count relay R160 also includes the contacts 153, 153, 144, 133, 122 and 119. When the line relay R120 then reoperates at the conclusion of the second digit 1, it interrupts, at the contacts 122, the previouslytraced circuit for energizing the winding of the rotary relay R150 and the previously-traced multiple path for short-circuiting the lower winding of the count relay R150. When the path mentioned for short-circuiting the lower winding of the count relay R160 is thus interrupted, there is completed a circuit, including the contacts and 35, for energizing in series the lower and upper windings of the count relay R160; whereby the latter relay operates through its second step, it being of the two-step type as previously noted. When the count relay R150 operates through its second step, it interrupts, at the contacts 163, a further point in the previouslytraced circuit for energizing the upper winding thereof; and prepares, at the contacts 164, a point in a circuit that is not employed in the present instance, but that is subsequently described for energizing the upper winding of the count relay R180. Also the count relay R160 completes, at the contacts 161, a circuit, including the contacts 195, 151, 1113 and 31, for operating the step relay R110. Upon operating the step relay R110 completes, at the contacts 112, a holding circuit, including the contacts 119, 161 and 195, for energizing the winding thereof; and prepares, at the contacts E11, a`

circuit traced hereinafter for operating the roiary magnet M154 of the Strowger mechanism 90. Y At the conclusion of the second digit l, the line relay R120 is retained in its operated position retaining operated the hold relay R130 so that the rotary relay R150 restores shortly thereafter, it being of the slow-to-release type. Upon restoring, the rotary relay R150 completes, at the contacts 152, the previously-mentioned circuit, in-

cluding the contacts 1li, 143 and 131, for operating the rotary magnet M194; whereby the wiper carriage of the Strowger mechanism is driven away from its normal rotary* position one step in the rotary direction so that the lower wiper digit l. Accordingly, theV used in an operationset I 9| and the upperwiper set |92 are moved together and respectively select the first outgoing trunks in the groups respectively including the outgoing trunks |92 and |93. However, in the present example, only the outgoing trunk in the group selected by the lower Wiper set I9! is tested by the switch through relay RI It by virtue of the circumstance that the lower wiper set I| is selected by the restored position of the count relay Ri. Also upon operating, the rotary magnet MEM interrupts, at the contacts I 95, the holding circuit for retaining operated the step relay RIFE. Upon restoring, the step relay Rll interrupts, at the contacts |72, a further point in the holding circuit for energizing the winding thereof; and interrupts, at the contacts I'II, the circuit for operating the rotary magnet M|94 so that the rotary magnet M |94 is restored.

More particularly, at this time ground potential, at the contacts |3I, is applied via the set of switch springs SI25, the winding of the switch through relay RI i and the contacts Ht and |88 to the hold wiper of the lower wiper set I 9i, whereby the switch through relay RI Iii performs the busy test noted. Specifically in the event the iirst outgoing trunk in the group including the outgoing trunk |92 is busy at this time, ground potential appears on the hold conductor thereof, whereby a path su'bstantially identical to that traced above is completed for short-circuiting the winding of the switch through relay RI iii so as to prevent operation of the latter relay. Also in this event, the application of ground potential upon the hold conductor of the lirst outgoing trunk mentioned completes a circuit, including the hold wiper of the lower wiper set |9I, the contacts |88, IIE, |5i and |95, for reoperating the step relay Rl'lil. Upon reoperating, the step relay RI l0 again completes, at the contacts |72, the holding circuit for energizing the winding thereof; and again completes, at the contacts I'I, the circuit for operating the rotary magnet Mme. Accordingly, it will be understood that the step relay RI'IU and the rotary magnet Mi9f2 interact to effect successive stepping of the wiper carriage of the Strowger mechanism |99 so long as busy outgoing trunks in the group, including the outgoing trunk m2, are encountered by the hold wiper of the lower wiper set I9 I.

When, however, an idle outgoing trunk in the group, including the outgoing trunk |02, in selected by the lower wiper set |9l, further operation of the Strowger mechanism |9i in the rotary direction is arrested by virtue of the absence of potential upon the hold conductor of the outgoing trunk noted. Specifically, in this case, absence of ground potential upon the hold conductor of the outgoing trunk noted prevents completion of the path for short-circuiting the Winding of the switch through relay RI Iii; and prevents completion of the direct circuit for energizing the winding of the step relay R| 1U. More specifically, in this case, a circuit, including the contacts |3I, the set of switch springs SIZE, and the contacts IBI and |95, is completed for energizing in series the winding of the switch through relay RI 0 and the winding of the step relay Rlll, When this series circuit is thus completed, the switch through relay RI Ill operates; however, the step relay RI'IE! does not operate as the latter relay is of the marginal type. Upon operating, the switch through relay RI II) completes, at the contacts I I8, a holding circuit, including the contacts |95, the set of switch springs S|25 and the 4contacts |3| for energizing the winding thereof lin series Further the switch through relay RI I0 at the contacts I6, a further point in the abovetraced testing circuit extending to the hold wiper of the lower wiper set ISI and completes, at the contacts ||1, a direct path, including the contacts |3| and |38, for applying ground potential to the hold wiper of the lower wiper set and consequently to the hold conductor of the selected outgoing trunk in the group, including the outgoing trunk |62. Further, the switch through relay RII 0 completes, at the contacts III, ||3, ||5 and II'I connections respectively including the contacts |52, IM, and |88 between the conductors of the incoming trunk IDI and the corresponding wipers or the lower wiper set |9I; and thus to the corresponding conductors o1 the selected outgoing trunk. Also the switch through relay RI I9 interrupts, at the contacts I 2 and 4, the loop circuits for energizing in series the upper and lower windings of the line relay RIZD in order to cause the latter relay to restore, Finally the switch through relay RI It interrupts, at the contacts H9, the circuit for retaining energized the winding of the hold relay RIM in order to cause the latter relay to restore shortly thereafter, it being of the slow-to-release type. Upon restoring, the hold relay RIS@ interrupts, at the contacts |35, the hol-dinfr circuit for retaining energized the lower winding of the count relay RIS!) in order to cause the latter relay to restore shortly thereafter, it being of the slow-to-release type. Further the hold relay Rlt interrupts, at the contacts 53|, the path for applying ground potential in the toll selector I El@ to the hold conductor of the incoming trunk I 0| and to hold the wiper of the lower wiper set |9| interrupts,

selector |99 is retained in its At this time, the toll selector IUE) has operated to select an idle outgoing trunk in the group, including the outgoing trunk |02, and has operated to complete a connection between the incoming trunk lill and the selected outgoing trunk; in the group noted. For reference purposes, it may be assumed that the toll selector It@ has operated to select the particular outgoing trunk |92 and has completed a connection between the incom ing trunk I 9| and the outgoing trunk I 92, whereby the toll selector I ilil is retained in its operated position by virtue of the application of ground potential upon the hold conductor of the incom` ing trunk IEBI in the preceding toll switch train.

At this time, one or more digits that may be received over the line conductors of the incoming trunk 9| proceed directly over the line wipers of the lower wiper set |9| and consequently over the line conductors of the outgoing trunk |92 to the succeeding toll switch train. Moreover any supervisory controls may be transmitted directly by virtue of the circumstance lector For example, answer and disconnect signals: may be returned over the line conductors or the control conductors of the outgoing trunk I U2 and consequently over the line conductors or the control conductor of the incoming trunk 0| and the,

with the winding of the step relay RIU,t

However, at this It!) occupies its switched-through position.

preceding toll switch train to the toll switchboard, not shown. Moreover should the succeeding toll switch train encounter an all-trunksbusy condition, 120 ground impulses per minute are applied to the control conductor of the outgoing trunk |02 and are returned over the connection via the control conductor of the incoming trunk |I so as to effect the return of an alltrunks-busy signal to the toll switchboard, not shown. Y

At the conclusion of the established connection, in response Yto a release that is performed over the preceding toll switch train, ground potential is removed Vfrom the hold conductor of the incoming trunk IOI, interrupting the holding circuit for energizing in series the winding of the switch through relay RI l0 and the winding of the step relay RI'I0 so as to cause the switch through relay RI I0 to restore. Upon restoring, the switchY through relay RI I8 completes, at the contacts |I9., a circuit, including the contacts |22 and |34 and the set of switch springs |23, for operating the release magnet Ml, whereby the wiper carriage of the Strowger mechanism |90 is released and returned to its normal rotary and vertical positions. When the Wiper carriage of the Strowger mechanism |99 is thus released, the sets of switch springs S|23 and S|2 are again operated.v Specically, the set of switch springs S|23 is operated to interrupt the circuit for retaining `operated the release magnet Mlti. Further the -switch through relay RI I8 interrupts, at the contacts II'I, the connection between the hold wiper of the lower wiper set |9I and the hold conductor of the incoming trunk liI so as to effect the release of the succeeding toll switch train. At this time, the toll selector |08 is completely released and available for further use.

Now assuming that a connection is to loe extended via the toll switch train, by way of the toll selector |00 and by way of one of the outgoing trunks in the group, including the outgoing trunk |03, the toll selector |00 is marked as idle to the preceding toll switch train by the absence of potential upon the hold conductor of the incoming trunk |0I and is seized in the manner previously explained effecting operation of the line relay YRI20, the hold relay R|38 and the transfer relay RI40. In this case, the toll select'or |00 receives digit 2, based upon the prior assumption that the toll selector |00 receives the first digit 1 and the second digit 1 in order to effect the selection of an idle outgoing trunk in the group including the outgoing trunkk |02. In response to the first digit 1, the toll selector |00 is operated in the manner previously explained, per wiper sets |9`| and |92 respectively select the groups of outgoing trunks respectively including the outgoing trunks |02 and |03. Now in the present case, when the line relay R|20 receives the second digit 2, it restores and reoperates twice in succession in accordance with the two impulses of the digitV 2. During the second digit 2, upon the first restoration of the line relay R528, the rotary relay R|50 is operated and the count relay R|60 is operated through its first step; then 'upon the first reoperation of the line relay R|28, the count relay RI00is operated through its second step; all in the manner previously explained. Now during the second digit, upon the second restoration of the line relay RI20, there is Vcompleted, at the contacts |22, a circuit, including the contacts I'I9, |33, |44, |53 and |84, for energiz'ing the upper winding of the count relay RI80 the first digit l and the second whereby the lower and upin order to cause the latter relay toV operate. Upon operating, the count relay R| completes, at the contacts |89, a holding circuit, including the contacts I3I, for energizing the lower winding thereof. Further the count relay RI 80 interrupts, at the contacts |82, |84, |86 and |88, the normal connections to the lower wiper set ISI; and completes, at the contacts IBI, |83, and |81, corresponding connections to the upper wiper set |92. Now at the conclusion of the second digit 2, the line relay RI20 is retained in its operated position; and shortly thereafter the rotary relay RI Sil restores, the latter relay being of the slow-tc-release type remaining operated during the second digit. Upon restoring, the rotary relay RI 50 completes, at the contacts |52, the circuit for operating the rotary magnet MISA, whereby the rotary magnet MI 94 cooperates with the step relay R|10 in the manner previously explained in order to cause the upper Wiper set |92 to select an idle outgoing trunk in the group including the outgoing trunk |03. For reference purposes, it may be assumed that the particular outgoing trunk |03 is selected by the upper wiper set |92, the outgoing trunk |03 being marked 'as idle by the absence of potential upon the hold conductor thereof, whereby the switch through relay RI |0 is operated in the manner previously explained in order to arrest further rotation :of the Wiper carriage of the Strowger mechanism |90 and to complete the connection between the incoming trunk IOI and the upper wiper set |92 and consequently the connection to the outgoing trunk |03 and thus to the succeeding toll switch train. When the toll selector |00 is operated into its switched-through position in the present case by operation of the switch through relay R| |0, the line relay RI20, the hold relay RI30, and the count relay RIBD restore in the manner previously explained. However, the switch through relay RI I0 is retained in its operated position by virtue of the application of ground potential upon the hold conductor of the incoming trunk |0I in the preceding toll switch train. Also this application of ground potential upon the hold conductor of the incoming trunk I0| completes a multiple holding circuit, including the contacts |89, for retaining'energized the lower winding of the count relay RI80 so that the latter relay is retained in its operated position, the count relay R|80 constituting a wiper switching relay, as previously noted.

At the conclusion of 'the established Aconneci tion, in response `to a release that is performed over the preceding toll switch train, ground potential is .removed from the hold conductor of the incoming trunk I0| effecting the release -of the toll selector |08 and train. Specifically, the removal of ground potential from the hold conductor of the incoming trunk |0| effects the Vrestoration of the switch through relay RI I0 and the `consequent release of the Strowger mechanism |90 in the manner previously explained. Also the count relay RI80 is restored so as to transfer, at the contacts |81 to |88, inclusive, the connections from the upper wiper set |92 to the lower wiper set |9'I. At this time, the toll selector V and available for further use.

Now assuming that a connection is to be extended via the toll switch Vtrain by way of `the toll selector |00 and by way. of one of the outgoing trunks in the trunk idle to the preceding toll switch train by the the succeeding toll switchV |00 is completely released group including the outgoingY |04, the toll selector |00 is marked asV absence of potential upon the hold conductor of the incoming trunk II and is seized in the manner previously explained effecting operation of the line relay RIZI), the hold relay RI3U and the transfer relay Rlliil. In this case, the toll selector ill@ receives a single digit, and for reference purposes, it may be assumed that the single digit is the digit 2. Specically, the line relay RI2D follows the single digit 2, causing the lower wiper set ISI to select in the lower contact bank the group of outgoing trunks, including the outgoing trunk Iilil, the upper wiper set |92, making no selection of outgoing trunks in the upper contact bank in its corresponding position. Also when the wiper carriage of the Strowger mechanism |39 is driven two steps in the vertical direction away from its normal vertical position, the set of switch springs S|28 is operated to complete a circuit, including the contacts I 3|, M2, |32 and I 9:5 for `operating the step relay RI'IQ. Upon operating the step relay Rl 'iii completes, at the contacts |l2, a holding circuit, including the contacts Ils and |32, the set of switch springs SIZ and the contacts |95, for energizing the winding thereof.

At the conclusion of the single digit 2, the line relay RIZil is retained in its operated position retaining operated the hold relay RI3i and effecting the restoration of the transfer relay RMI) shortly thereafter, the latter relay being of the slow-to-release type. Upon restoring, the transfer relay R|4i completes, at the contacts |43, a circuit, including the contacts Itl, |52 and IlI, for operating the rotary magnet MIM, whereby the wiper carriage of the Strowger mechanism Ig is driven one step in the rotary direction away from its normal rotary position. Also the rotary magnet MIM interrupts, at the contacts |95, the holding circuit for retaining operated the step relay RI lil in order to cause the latter relay to restore and interrupt, at the contacts Ill, the circuit for operating the rotary magnet MMM. Accordingly the rotary magnet MI 913 and the step relay RI l@ interact in the previously-described manner, in order to drive the wiper carriage of the Strowger mechanism i9!) step-by-step in the rotary direction so that the lower wiper set ISI may search for an idle outgoing trunk in the group including the outgoing trunk |94. When the lower wiper set |95 selects an idle outgoing trunk, such, for example, as the outgoing trunk mi in the group noted, no potential is encountered by the hold wiper of the lower wiper set IBI, since the idle outgoing trunk |34 is marked as idle by the absence of potential upon the hold conductor thereof. ln passing, it is noted that the presence of ground potential upon the hold conductor of a busy outgoingT trunk in the group noted causes the application of ground potential to the hold wiper of the lower wiper set |9| so as to complete an alternative circuit, including the contacts |38, Ht and |32, the set of switch springs S|28 and the contacts Is for reoperating the step relay Rltl. However when the idle outgoing trunk Isl-l is selected by the lower wiper set |95, the above-traced circuit is not completed; whereby an alternative circuit is completed for energizing the winding of the switch through relay RiIi in series with the winding of the switch through relay RIIc in series with the winding of the step relay RIM. The last-mentioned circuit extends from ground by way of the contacts 3L the set of switch springs SIZ, the winding of the switch through relay RHS, the contacts 32, the set of switch 1 springs S |28, the contacts |95, and the winding of the step relay Rllil to battery. When this circuit is completed, the switch through relay RI I0 operates but the step relay RIlEl does not operate as it is of the marginal type. through relay RiIiB thus operates, further roto that previously explained. In this case, when is released and returned to its normal rotary and vertical positions, the set of switch springs SIN is operated to its open position. .At this time, the toll selector lili! is completely released and is available for further use.

incident to the operation of the toll selector Silit to select an idle outgoing trunk oi the groups respectively including the outgoing trunks iil, Ist and ist, it may occur that all of the outgoing trunks in the particular group are busy. Specifically fcllowing the two digits l and l, all of the outgoing trunks in the group including I t2 may be tested as being two digits l and 2, all of the outgoing trunks in the group including the outgoing trunk |03 may ybe tested as being busy; and following the signal digit 2, all of the outgoing trunks in the group including the outgoing trunk llfl as being busy. In any Strowger mechanism continues until the driven eleven steps in busy; following the case, operation of the |86 in the rotary direction wiper carriage thereof is the rotary direction away from its normal rotary position, whereby the sets of switch springs SM5, :SIEE and SI2? are operated. More particularly, the set of switch springs cdl'it is operated to its open position in order positively to prevent operation of the switch through relay Ritt; the set of switch springs liil is operated into its closed position in order to complete a path, including the contacts I 3 I, for applying ground potential to the alarm conductor C537; and the set of switch springs SI2? is operated into its closed position in order to complete a connection including the resistor |3lI between the busy conductor Clli and the control conductor of the incoming trunk itl. The application of ground potential to the alarm conductor C531? is effected to bring about an alarm after a predetermined time interval; and in passing, it is noted that this alarm is brought about in. the event the transfer relay RI 4t is retained in its operated position for the time interval mentioned following seizure of the toll selector Imi. ciiically the 'transfer relay RIE@ completes, at the contacts Mii, a path for applying ground potcntional to the larin conductor @|37 during the short time interval that the transfer relay Ridi) occupies its operated position following seizure of the toll selector ill@ and prior to the reception of the digit. Ground impulses at a rate of per minute are applied to the busy conductor CI 35 in order to bring about corresponding flashing of supervisory equipment associatedwith the toll mi, thereby to effect the release the outgoing' trunky may be tested operator position connected to the preceding toll switch train so as to render to the operator thereat an all-trunks-busy supervision. Upon receiving the busy supervision noted when the toll selector 00 encounters the all-trunks-busy condition, the operator at the toll switchboard performs a release control over the preceding toll switch train so as to effect the restoration oi the line relay R120 and the consequent restoration of the hold relay RI30 shortly thereafter. Upon restoring, the hold relay RI30 completes, at the contacts |34, the previously-traced circuit for operating the release magnet MI so as to effect the release of the Strowger mechanism i90 in the manner previously explained. Also upon restoring, the hold relay R130 interrupts, at the contacts I3I, the path for applying ground potential in the toll selector I00 to the hold conductor of the incoming trunk IOI in order again to mark as idle the toll selector |00 to the preceding toll switch train.

Referring now more particularly to Fig. 2, the toll selector repeater 200 there illustrated and embodying the features of the present invention is of the combination one-digit and twodigit type. The selector repeater 200 comprises a Strowger mechanism 300 including a lower wiper set 30I and an upper set 302, as well as lower and upper contact banks respectively accessible to the two wiper sets noted; each of the contact banks comprises a plurality and maximum of ten'vertically spaced-apart levels or rows of individual contact sets disposed in spaced relation in the rotary direction; and certain of the levels of ccntact sets in the respective lower and upper ccntact banks arepaired so that the respective lower and upper wiper sets 30| and 302 have simultaneous access thereto.

Further, the toll selector repeater` 200 occupies an intermediate position in a toll switch train, and further includes an incoming trunk l that is accessible to preceding toll switching apparatus, not shown, that is, in turn, accessible .to a toll operator switchboard, not shown. Also the contact sets provided in the various levels of the lower and upper contact banks terminate groups of trunks extending to succeeding toll switching apparatus, not shown. The portions of the toll switch train preceding and succeeding the toll selector repeater 200 have not been illustrated in the interest or brevity.

Specifically in ger mechanism 300, the lower wiper set has access to a level of contact sets terminating a group of outgoing trunks 202, etc., and the upper wiper set 202, etc., has access to a level of contact sets terminating a group of outgoing trunks 203, etc., these levels in the respective lower and upper contact banks being paired with respect to each other so that the respective lower and upper wiper sets 30| and 302 have simultaneous access to the outgoing trunks 202 and 203.` Also the lower contact bank of the Strowger mechanism 300 comp-rises a level of contact sets terminating a group of outgoing trunks 204,'etc., and a level of contact sets terminating a group of outgoing trunks 205, etc., both accessible to the lower wiper set 30|. In the toll selector repeater 200, the incoming trunk 20| comprises a pair of line conductors, a hold conductor, and ductor respectively marked C and EC. Also each of the outgoing trunks 202, etc., comprises a pair of line conductors, a hold conductor and a control conductor.

` Further the Strowger mechanism 300 com.-

the contact banks of the Strow-v a control con- .12 prises a vertical magnet M303 for driving the wiper carriage, mounting the lower and upper wiper sets 30| and 302, step-by-step in the vertical direction away from its normal vertical position, a rotary magnetY M304 for driving the wiper carriage step-by-step in the rotary direction away from its normal rotary position, and a release magnet M300, for releasing the wiper carriage and for causing it torbe returned to its normal rotary and vertical positions. Also associated with the wiper carriage of the Strowger mechanism 300 are two sets of switch springs S30I and S302 that are operated when the wiper carriage is moved one step in the vertical direction away from its normal vertical position, and two sets of switch springs S303 and S304 that are operated when the wiper carriage is moved eleven steps in the rotary direction away from its normal rotary position. Finally a set of switch springs S305 is associated with the wiper carriage of the Strowger mechanism 300 that is operated when the wiper carriage is moved in the vertical direction predetermined numbers of steps corresponding to the level of the group of trunks 204, etc., appearing before the lower wiper set 30I or corresponding to the level of the group of trunks 205, etc., appearing before the lower wiper set 301, as well as a set of switch springs S306 that is operated when thewiper carriage is moved in the vertical direction a predetermined number of steps corresponding to the level of the group of trunks 205, etc., appearing before the lower wiper set 305. Finally the toll selector repeater 200 comprises a repeating unit including inductively coupled primary coils 22e` and 228 andsecondary coils 221 and 22S, as well as a relay group including a repeater cutout relay R2 I 0, an answer relay R220, a supervisory relay R230, a switch through relay R220, a line relay R250, a hold relay R260, a transfer relay R210, a rotary relay R215, a count relay R230, a step relay R285, and a count or wiper switching relay R290.

First assuming that a connection is to be extended vial the toll switch train by way of the toll selector repeater 200 and by way of one of the outgoing trunks in the group including the outgoing trunk 202, the toll selector repeater 200 is marked as idle to the preceding toll switch train by the absence of potential upon the hold conductor of the incoming trunk 20I extending thereto. When the precedingr toll switch train seizes the toll selector repeater 200 via the incoming trunk 201, ground potential is applied to the hold conductor of the incoming trunk 201, and a circuit is completed for energizing the upper winding of the line relay R250 in order to cause the latter relay to operate. Specically, battery potential in the preceding toll switch train is applied to the control conductor of the incoming trunk 201 completing the above-mentioned circuit to ground potential in the toll selector repeater 200 and including the contacts 2I1 and 234, as well as the upper winding of the line relay R250. Upon operating the line relay R250 completes, at the contacts 252, a circuit, including the contacts 2 I 3, for operating the hold relay R260. Upon operating, the hold relay R260 completes, at the contacts 203, a path for applying ground potential to the hold conductor of the incoming trunk 20I in order further to retain operated the preceding toll switch train. Further the hold relay R260 completes, at the contacts 20|, a circuit for energizing the right-hand winding of the answer relay R220, and a multiple circuit, including the set of switch springspoint in the circuit S302, for energizing the lower winding of the transfer relay R212. The answer relay R220 is of the polarized type, and does notoperate incident to energization of the right-hand winding thereof until the left-hand winding thereof is energized in a predetermined direction. However the transfer relay R210 operates.

At this time, the rst digit is received over the control conductor of the incoming trunk 22! in order to cause the line relay R259 to follow; and it may be assumed that this first digit is the digit l. Accordingly the line relay R250 restores and then reoperates interrupting and then recomplcting, at the contacts 252, the circuit for retaining operated during irnpulsing the hold relay R250, the latter relay being of the slow-to-release type. Also the line relay R252 completes and then interrupts, at the contacts 253, a multiple circuit, including the contacts 219, 265, and 212, for energizing the upper winding of the transfer relay R212 and for operating the vertical magnet M303 of the Strowger mechanism 322 in order to retain the transfer relay R212 in its operated position during impulsing, as it is of the slow-torelease type, and in order to operate the vertical magnet M303 so as to drive the wiper carriage of the Strowger mechanism one step in the vertical direction away from its normal vertical position. When the wiper carriage of the Strowger mechanism 300 is thus driven one step in the vertical direction away from its normal vertical position the sets of switch springs Stili and S222 operate. Speciiically the set of switch springs S30I is closed to prepare a circuit traced hereinafter for operating the release magnet M325 of the Strowger mechanism 360; and the set of switch springs S302 is opened in order to interrupt the circuit for energizing the lower winding of the transfer relay R210. Also when the wiper carriage of the Strowger is driven one step in the vertical direction away from its normal vertical position the lower and upper wiper sets 30| and 322 are moved together so that they respectively select the two groups of outgoing trunks respectively including the outgoing trunks 202 and 203. In passing, it is noted that the count relay R295 normally occupies its restored position so that the lower wiper set 3i!! is normally effectively selected at the contacts 292, 294, 29B and 229.

At the conclusion of the nrst digit l, the line relay R250I is retained in its operated position in order to retain operated the hold relay R252 so that the transfer relay R210 restores shortly thereafter, the latter relay being of the slow-torelease type. Upon restoring, the transfer relay R210 interrupts, at the-contacts 211i,- a further magnet M303 and prepares at the contacts 213, a point in a circuit traced hereinafter for energizing the winding of the rotary relay R215.

I When the second digit is received, the line relay R25i again follows; and in the present instance, the second digit is the digit 1. Accordingly line relay R250 restores and then reoperates retaining operated the hold relay R252 during impulsing as it is of the slow-to-release type. Also the line relay R250 upon restoring completes, at the contacts 253, the previously mentioned circuit, including the contacts 219, 265, 213 and 23l for energizing the winding of the rotary relay R215, as well as a multiple circuit, including the contacts 243 and 28|, for energizing the upper winding of the count' relay- R235. 'The rotary relay R215 operates to complete, at the mechanism 325 for operating the vertical' contacts 21B, a path including the resistor 233 for" short-circuiting the left-hand winding of the answer relay R220 and the windings 221 and 229 of the repeating unit 225 for a purpose more fully explained hereinafter. The count relay R230 operates only through its first step; this relay being of the two-step type. Upon. operating through its first step, the count relay R280 completes, at the contacts 233, a path, including the contacts 251, for short-circuiting the lower winding thereof. The path for short-circuiting the lower winding of the count relay R280 also includes the contacts 281, 243, 23|, 213, 285, 253 and '212. When the line relay R250 then reoperates at the conclusion of the second digit l, it interrupts, at the contacts 253, the previously traced circuit for energizing the winding of the rotary relay R215 and the previously traced multiple path for short-circuiting the lower wind-` ing of the count relay R230. When the path mentioned for short-cirouiting the lower winding of the count relay R280 is thus interrupted, there is completed a circuit, including the contacts 25| and 233, for energizing in series the lower and upper windings of the count relay R282; whereby the latter relay operates through its second step, it being of the two-step type as previously noted. When the count relay R280 operates through its second step, it interrupts, at the contacts 2st, a further point in the previously traced circuit for energizing the upper winding thereof, and prepares, at the contacts 282, a point in a circuit that is not employed in the present instance, but that is used in an operation subsequently described for energizing the upper winding of the count relay R290. Also the count relay R20@ completes, at the contacts 232, a circuit, including the contacts 305, 211, 212, 225 and 263, for operating the step relay R285. Upon operating the step relay R285 cornpletes, at the contacts 221, a holding circuit, including the contacts 2653', 284 and 305, for energizing the winding thereof; and prepares, at the contacts 285, a circuit traced hereinafter for operating the rotary magnet M304 of the Strowger mechanism 300.

At the conclusion of the second digit l, the line relay R252 is retained in its operated position retaining operated the hold relay R222 so that the rotary relay R215 restores shortly thereafter, it being of the slow-to-release type. Upon restoring, the rotary relay R215 completes, at the contacts 218, the previously mentioned circuit, including the contacts 28B, 212, 242 and 283, for operating the rotary magnet M304; whereby the wiper carriage of the Strowger mechanism 300 is driven away from its normal rotar-yposition one step in the rotary direction so that the lower wiper set 3M and the upper wiper set 322 are moved together and respectively select the first outgoing trunks in the groups respectively including the outgoing trunks 222 and 203. However, in the pre-sent example, only the outgoing trunk in the group selected by the lower wiper set 2G! is tested by the switch through relay R242 by virtue of the circumstance that the lower piper set 353i is selected by the .restored position of the count relay R222. Also upon operating, the rotary magnet M2M interrupts, at the contacts 525, the holding circuit for retaining operated the step relay R285. Upon restoring, the step relay R285 interrupts, at the contacts 201, a further point in the holding circuitfor energizing the winding thereof; and interrupt-l ing, at'the' contacts 286, the' circuit for operating the rotary magnet M304 so that the rotary magnet M304 is restored.

More particularly, at this time, ground potential,` atv the contacts 263, is applied via the righthand contact of the set of switch springs S304, the winding of the switch through. relay R240 and the contacts 24| and 200 to the hold wiper of the lower wiper set 30|; whereby the switch through relay R240 performs the busy test noted. Specically, in the event the rst outgoing trunk in the group, including the outgoing trunk 202 is busy at this time, ground potential appears on the hold conductor thereof, whereby a path substantially identical to that traced above is completed for shrt-circuiting the winding of the switch through relay R240 so as to prevent operation of the latter relay. Also in this event, the application of ground potential upon the hold conductor of the first outgoing trunk mentioned completes a circuit, including the hold wiper of the lower wiper set 30|, the contacts 200, 24|', 284 and 305, for reoperating the step relay R285. Upon reoperating, the step relay R205 -again completes, at the contacts 281, the holding circuit for energizing the winding thereof; and again completes, at the contacts 206, the circuit for operating the rotary magnet M304. Accordingly, it will be understood that the step relay R285 and the rotary magnet M304 interact to effect successive stepping of the wiper carriage of the Strowger mechanism 300 so long as busy outgoing trunks in the group, including the outgoing trunk 202, are encountered by the hold wiper of the lower wiper set 30|.

When, however, an idle outgoing trunk in the group, including the outgoing trunk 202, is selected by the lower wiper set 30|, further operation of the Strowger mechanism 300 in the rotary direction is arrested by virtue oi the absence oi potential upon the hold conductor of the outgoing trunk noted. Specifically, in this case, the absence of ground potential upon the hold conductor oi the outgoing trunk noted prevents completion o the path for short-circuiting the winding of the switch through relay R240; and prevents completion of the direct cir-V cuit ior energizing the winding of the step relay R285. More speciiically, in this case, a circuit, including the contacts 203, the right-hand contacts of the set of switch springs S304 and the contacts '284 and 305, is completed for energizing in series the winding of the switch through relay R240 and the winding oi the step relay R235. When this series circuit is thus completed, the switch through relay R240 operates; however, the step relay R235 does not operate as the latter. relay is of the marginal type. Upon operating, the switch through relay R240 completes, at the contacts 242', a holding circuit, includingv the contacts 305, the right-hand contacts of the set of switch springs S304 and the contacts 203 for energizing the winding thereof in series with the winding of the step relay R205. Further the switch through relay R240 interrupts, Vat the contacts 24|', a further point in the above traced test circuit extending to the hold wiper of the lower wiper set 30|; and completes, at the contacts 249, a direct path, including the contacts 298, ior applying ground potential to the hold wiper of the lower wiper set 30| and consequently to the hold conductorV of the selected outgoing trunk in the group, including the outgoing trunk 202. AFurther theV switch through relay'R240 completes, at` the contacts 24| and '244, a connection, including the contacts 2|| and 2|4 between the series connected windings 226 and 228 of the repeating unit 225 and the line conductors of the incoming trunk 20|; and completes, at the contacts 242 and 245, a connection, including the contacts 2|3, 25|, 2|G, 202 and 294, between the series connected windings 221 and 229 of the repeating unit 225 and the left-hand winding of the answer relay R220, and the line wipers of the lower wiper set 30|. Also the switch through relay R240 completes, at the contacts 240, a connection, including the contacts 2|8' and 206, between the winding of the supervisory relay R230 and the control wiper of the lower wiper set 30|.

At this time, the left-hand winding of the answer relay R220 is connected in series relation with the windings 221 and 220 of the repeating unit 225 and is thus bridged across the line wipers of the lower wiper set 30| andV consequently across the line conductors of the selected outgoing trunk in the group, including the outgoing trunk 202. For reference purposes, it may be assumedthat the particular outgoing trunk 202 is selected at this time, whereby the succeeding toll switch train is seized as a consequence of the bridging of the left-hand winding of the answer relay R220 across the line conductors thereof and the direct application of ground potential to the hold conductor thereof, so that the succeeding switch train is conditioned to receive a digit repeated thereto from the toll selector repeater 200. In passing, it is noted that incident to the restoration of the, rotary relay R215, at theV conclusion of the second digit, there is interrupted, at the contacts 215, the previously mentioned path for shortcircuiting the left-hand winding of the answer relay R220 and the windings '221 and 229 of the repeating unit 225. VWhile the left-hand winding of the answer relay R220 is energized at this time, the latter relay is not poled to operate, it eing of the polarized type. At this time, the t ll selector repeater 200 has operated to select the outgoing trunk 202 in order to effect seizure of the succeeding switch train and the toll selector repeater 200 has switched through and is in readiness to repeat over line conductors of the outgoing trunk 202 one or more digits received over the control conductor of the incoming trunk 20|.

Now assuming that a digit is received over the control conductor of the incoming trunk 20|, the line relay R250 follows retaining the hold relay R200 in its operated position as the latter relay is of the slow-to-release type. Also each time the line relay R250 restores and then reoperates, it completes and then interrupts, at the contacts 253, the previously traced circuit for energizing the winding of the rotary relay R215 in order to cause the latter relay to operate and remain operated during impulsing as it is of the slowto-release type. Upon operating, the rotary relay R215 completes, at the contacts 21B, the path for short-circuiting the left-hand winding of the answer relay R220 and the windings 221 and 220 of the repeating unit 225 in order to improvev impulsing over the line wipers of the lower wiper set 30|. Further each time the line relay R250 restores and then reoperates it interrupts and then recompletes, at the contacts 25|, the impulsing path,V including the contacts 202, 242, and 2 3, the resistor 223 and the contacts 216, 2|6, 245 and 290,v extending between the linewpers -of thev lower Vwiper set 30| an consequentlybe-y tweenl the line conductors ofthe outgoing trunk;

202 in order to control the operation of the succeeding switch train. Thus it will be understood that a digit received over the control conductor of the incoming trunk 20| by the toll selector repeater 200 is repeated at this time over the line conductors of the outgoing trunk 202 to the succeeding switch train in order to effect operation thereof. In respons-e to one or more digits repeated by the toll selector repeater 200 over the outgoing trunk 202, the succeeding switch train extends the connection to its destination; and when the call is answered the succeeding switch train operates to effect the reversal of battery potential over the line conductors of the outgoing trunk 202, whereby the left-hand winding of the answer relay R220 is poled to operate, the rotary relay R2l5 having restored shortly following the conclusion of any digit that is repeated by the toll selector repeater 200. Upon operating, the answer relay R220 completes, at the contacts 22|, a circuit for operating the supervisory relay R230. Upon operating, the supervisory relay R230 interrupts, at the contacts 23|, a further point in the circuit for energizing the winding of the rotary relay R2 i5 interrupting, at the contacts 234, the previously traced circuit for energizing the upper Winding of the line relay R250; and completes, at the contacts 233, an alternative circuit, including the contacts 2 Il, for energizing in series the lower and upper windings of the line relay R250. More specically, upon operating, the supervisory relay R230 disconnects the upper low resistance winding from the control conductor of the incoming trunk 20| and connects in series the lower high resistance winding and the upper low resistance winding of the line relay R250 to the control conductor of the incoming trunk 20| whereby the resistance from the ground potential applied to the control conductor of the in- .coming trunk 20| is changed from low to high.

This change in resistance from ground potential that is applied to the control conductor of the incoming trunk 20| incident to operation of the answer relay R220 as a consequence of answering of the extended connection comprises an answer signal that is transmitted over the control conductor of the incoming trunk 20| and the preceding toll switch train to the toll operator switchboard and is appropriately converted into an answer signal at the toll operator switchboard.

At the conclusion of the established connection, when the called destination performs a release operation, the succeeding tollswitch train again reverses the polarity of the line conductors of the outgoing trunk 202, whereby the answer relay R220 restores eiecting the restoration of the supervisory relay R230.v Upon restoring, the

trunk 20|, whereby lower resistance ground potential is substituted for higher resistance ground potential as a consequence of the exclusion of the lower high resistance winding of the line relay R250 so that a disconnect signal is returned over the control conductor of the incoming trunk 20| in order to render to the toll operator switchboard via the preceding toll switch train, a correspending disconnect signal.

The operator at the toll switchboard effects the release of the preceding toll switch train, whereby ground potential is removed from the hold conductor of the incoming trunk 20|, and battery potential is removed from the control conductor of the incoming trunk 20| eiecting the restoration of the line relay R250. Upon restoring, the line relay R250 interrupts, at the contacts 25|, the loop circuit extending via the line conductors of the outgoing trunk 202 to the succeeding switch train in order to effect the release thereof. Also the line relay R250 interrupts, at the contacts 252, the circuit for retaining operated the hold relay R260 in order to cause the latter relay to restore shortly thereafter, it being of the slow-to-release type. Upon restoring, the hold relay R260 completes, at the contacts 256, a circuit, including the contacts 2|9, 253, 245 and the set of switch springs S30I,

I' for operating the release magnet M306; whereby the wiper carriage of the Strowger mechanism 300 is released and returned to its normal rotary and vertical positions. When the wiper carriage of the Strowger mechanism 300 is thus released, the sets of switch springs SSM and S302 are operated. Specifically, the set of switch springs 830| is opened to interrupt the circuit for operating the release magnet M306; and the set of switch springs S302 is closed to prepare the circuit for energizing the lower winding of the transfer relay R210. Further the hold relay R260 interrupts, at the contacts 263, the holding circuit for retaining operated the switch through relay R240 and the multiple path for applying ground potential to the hold conductor of the incoming trunk 20| in order again to mark the incoming trunk 20| as idle to the preceding toll switch train. Upon restoring, the switch through relay R240 interrupts, at the contacts 249, the path for applying ground potential to the hold wiper of the lower wiper set 30|; and upon restoring, the hold relay R260 interrupts, at the contacts 25|. the holding circuit for retaining operated the count relay R280 and the multiple circuit for energizing the right-hand winding of the answer relay R220. At this time, the toll selector repeater 200 is completely released and available for further use.

Reconsidering the extension of the connection via the toll switch train by way of the toll selector repeater 200, it will be understood that should the succeeding toll switch train encounter an all-trunks-busy condition following operation of the toll selector repeater 200 into its switchedthrough position, that 120 ground impulses per minute are returned over the control conductor ofthe outgoing trunk 202 so as to complete a direct circuit, including the contacts 296, 246 and 2|8', for energizing the supervisory relay R230 so as to cause the latter relay to operate and restore intermittently. Each time the supervisory relay R230 operates and restores, it changes.

. at the contacts 233 and 234, the resistance in the ground connection via the upper winding of the line relay R250 or via the upper and lower windings of the line relay R250 to the control conductor of the incoming trunk 20| so as to return the all-trunks-busy signal to the toll switchboard in a manner substantially identical to the return of other supervisory signals thereto, as

explained above.

Now assuming that a connection is to be extended via the toll switch train by way of the toll selector repeater 200 and by way of one of the outgoing trunks in the group, including the outgoing trunk 203, the toll selector repeater 200 is marked as idle to the preceding toll switch train by the absence of potential upon the hold conductor of the incoming trunk 20| and is seized in vthe manner vprevioihisly ,"operation of the line relay :R259 andthe transfer relayV R210, as well as the yenergization Yof the `answer relay R225. ln this case, the toil selector repeater 200 receives the v ond digit 2, based upon the prior assumption that Vthe toll selector repeater 250 receives the rst Atheselection of e lgroup including the outgoing trunk 202. response to the rst digit 1, repeater 220 is operated in the manner previously fcaSe, When the linerelay `between theuwindings Ving unit 225 and the left-hand windings of the line wipers of the explained effecting R250, thehOlcl relai7 right hand winding of the first digit 1 andthe secdigitl and theseccnd digit 1 in order to effect an idle outgoing trunk in the In the V toll selector explained, whereby the lower and upper wiper isets 30| and 352 respectively select the groups of outgoing trunks respectively including the outgoing trunks 202 and 203. Now in the present R250 receives the second digit 2, it restores and reoperates twice in v.succession in accordance with the two impulses of the digit 2. During the second digit z,` upon the rst restoration of the line vrelay R253, the

rotary relay R215 is operated and the count relay R260 is operatedthrough its vrst step; then upon the Yiirst reoperation of the line relay R250, the

count relay R289 is operated through its second :step: vall in the manner previously explained.

Now rduring the. second digit, upon the second restoration of theline relay R250, there is completed, at the contacts 253, a circuit, including the contacts29, 255, 213, 23|, 243 and 282, for energizing the upper winding of the count relay R290 lin order to rcause the latter relay to operate. VUpon operating, the count relay R290 completes, at the contacts 2 1, a holding circuit, conta'ts 213, for energizing the there f. Further, the count relay the contacts 292, 294, 296 and including the lower winding R290 interrupts, at

299the normal connections to the lower wiper set-430|; Vand completes, at the contacts 29|, 293, 295 and'298, corresponding connections to the upper wiper set 302. Now at the'conclusion of the second digit 2, the line relay R259 is retained in its operatedfpoition: and shortly thereafter the rotary relay R215 restores, the latter relay being of the slow-to-re'ease type remaining operated .during the second digit. Upon restoringthe Vrotary relay R215 completes, at the contacts 218, the circuit for operatng the rotary magnet M304,

whereby the rotary magnet M304 cooperates with r the step relay R285 in the manner previously explained in order to cause the upper wiper set 302 to select an idle outgoing trunk in the group including the outgoing trunk 293. For reference vpurposeeit may be assumed that the particuanswer relay R229'and the upper wiper set 302, and to complete the connection between the ground potential and the hold wiperof the upper wiper set 392. Of course, the

connections mentioned are extended via the various wipers of the upper wiper set 302 to the cor- Cial the lower Wiper set 39| vresppndirle ,conductors fthe outgolns-trunkw and thus to the succeedingvtoll switch train. When the toll selector repeater v200 is operated into its switched-through position, in the present case `by operation of the switch througnrelay R240, the line relay R259, the hold relay'RZO. and the count relays R280 and R290 are retained in their operated positions.

The subsequent operation of the toll selector repeater 200 to repeat one or more digitsrover the selected outgoing truni 203 are the same as previously described. Moreover, the subsequent Vcontrol of the answer relay R220 and the supervisory relay R230 so as to effect the return of corresponding supervsory signals to the toll switchboard, not shov` n, are the same as previously explained.

lAt the conclusion of the established connection, in response to a release that is performed overthe preceding toll switch train, the line-relay R250 is restored so as to effect the release of the toll selector repeater 2d) and the succeeding toll switch train in a manner substantially identical tothat previously explained. Specifically upon restoring, the line relay R250 eiects the restoration of the hold relay R25J shortly thereafter, whereby the latter relay interrupts, at the contacts 263, the holdng circuit for energizing the lower winding of the count relay R290 so that the latter relay is restored. The Strowger mechanism 300 is released in the manner previously explained; and upon rest-ring, the count relay R290 transfers, at the contacts 29|, 292, 293, 294, 295, 293, 298 and 2 9, the connections from the upper wiper set 952 to the lower wiper set 30|. At this time, the toll seector repeater 200 is completely released and available for further use.

Now assuming that a connection is to be extended via the toll switch train by way of the toll selector repeater 200 and by way of one of the outgoing trunks in the group including the outgoing trunk 2 4, the toll selector repeater 200 is marked as idle to the preceding toll switch train lby the absenceY or poential upon the hold conductor of the incoming trunk 20| and is seized in the manner previously explained effecting operation of the line relay R250, the hold relay R250, and the transfer relay R210, as well as theenergization of the right-hand winding of the answer relay R222. In this case, the toll selector repeater 200 receives a single digit, and for reference purposes, it may be assumed that the single digit is the digit 2. Speciically, the line relay R250 follows the single digit 2 causing to select in the lower contact bank the group of outgoing trunks, including the outgoing trunk 204, the upper Wiper set 332 making no selection of outgoing trunks in the upper contact bankin its corresponding position. Also when the wiper carriage of the Strowger mechanism 300 is driven two steps in the vertical direction away from its normal vertical position, the set of switch springs S395 is operated to complete a circuit, including the contacts 305, 294, 21|, 248 and 253, for operating the step relay R285. Upon operating, the step relay R285 completes, at the contacts 291, a holding circuit, including the contacts 243 and 294, the set of switch springs S305 and the contacts 305, for energizing the winding thereof.

At the conclusion of the single digit 2, the line relay R259 is retained in its operated position retaining operated the hold relay R250 and eiecting `the restoration ofthe transfer relay R210 shortly thereafter, the latter relay being ofthe upon the hold conductor thereof.

fslow-to-releasetype. Upon restoring, the transfer relay R210 completes, at the contacts 212, a circuit, including the contacts 206, 218, 248 and 263, for operating the rotary magnet M304; whereby the Wiper carriage of the Strowger mechanism 300 is driven one step in the rotary direction away from its normal rotary position. Also the rotary magnet M554 interrupts, at the contacts 355, the holding circuit for retaining operated the step relay R285 in order to cause the latter relay to restore and interrupt, at the contacts 236, the circuit for operating the rotary magnet M304. Accordingly, the rotary magnet M304 and the step relay R255 interact in the previously-described manner in wiper carriage of the Strowger mechanism 350 step-by-step in the rotary direction so that the lower wiper set 39| may search` for an idle outgoing trunk in the group including the outgoing trunk 254. When the iower wiper set 30| selects an idle outgoing trunk, such, for example,

r as the outgoing trunk 2M in the group noted, no

potential is encountered by the hold wiper of the lower wiper set 35| since the idle outgoing trunk 204 is marked as idle by the absence of potential In passing, it is noted that the presence of ground potential upon the hold conductor of a busy outgoing trunkin the group noted causes the application of ground potential to the hold wiper of the lower wiper set 30| so as to complete an alternative circuit, including the contacts 209, 24| and 264, the set of switch springs S305 and the contacts 305, for reoperating the step relay R285. However, when the idle outgoing trunk 204 is selected by the lower wiper set 30|, the above traced circuit is not completed, whereby an alternative circuit is completed for energizing the winding of the switch through relay R245 in series with the winding of the step relay R235. The last mentioned circuit extends from ground by way of the contacts 253, the right-hand contacts of the set of switch springs S304, the winding of the switch through relay R240, the contacts 264, the set of switch springs S305, the contacts 305 and the winding of the step relay R285 to battery. When this circuit is completed, the switch through relay R245 operates, but the step relay R285 does not operate as it is of the marginal type. When the switch through relay R242 is thus operated, further rotation of the Wiper car- .riage of the Strowger mechanism 300 is arrested and the toll selector repeater 220 is switchedthrough in the manner previously explained effecting a connection between the incoming trunk 253| and the repeating unit 225 and a connection between the repeating unit 225 and the lower wiper set 30| and consequently via the selected outgoing trunk 224 to the succeeding toll switch train. The repeating of digits by the toll selector repeater 200 that are received over the control conductor of the incoming trunk 20| over the line conductors of the outgoing trunk 204 as well as the operation thereof in response to the various supervisory signals are the same as previously described. At the conclusion of the established connection and in response to a release that is performed over the preceding toll switch train, the toll repeater Eile is released, as well as the succeeding switch train; all in the manner previously explained. At this time, the toll selector repeater 22e is completely released and is available for further use.

Now assuming that a connection is to be extended via the toll switch train by Way of the toll order to drive the Till selector repeater 200 and by way of one of the outgoing trunks in the' group including the outgoing trunk 205, the toll selector repeater 280 is marked as idle to the preceding toll switch train by the absence of potential upon the hold conductor of the incoming trunk 20| and is seized in the manner previously explained effecting operation of the line relay R250, the hold relay R250 and the transfer relay R210, as Well as the energization of the right-hand winding of the answer relay R220. In this case, the toll selector repeater 200 receives a single digit, and for reference purposes, it may be assumed that the single digit is the digit 3. Specically, the line relay R250 follows the single digit 3 causing the lower wiper set 35| to select in the lower contact bank the group of outgoing trunks, including the outgoing trunk 255, the upper wiper set 322 making no selection of outgoing trunks in the upper contact bank in its corresponding position. Also when the wiper carriage or" the Strowger mechanism 300 is driven three steps in the vertical direction away from its normal vertical position, both the set oi switch springs S305 and the set of switch springs S306 are operated. The set of switch springs S305 is closed to prepare a circuit for operating the repeater cutout relay R2l; While the set of switch springs S305 is closed to complete the previously-traced circuit for operating the step relay R285. Upon operating, the step relay completes, at the contacts 281, the previouslytraced holding circuit for energizing the Winding thereof.

At the conclusion of the single digit 3, the line relay R250 is retained in its operated position retaining operated the hold relay R260 and effecting the restoration of the transfer relay R210 shortly thereafter, the latter relay being of the slow-torelease type. Upon restoring, the transfer relay R210 completes, at the contacts 212, the previously-traced circuit for operating the rotary magnet M304; whereby the rotary magnet M304 and the step relay R285 interacted in the manner previously explained in order to cause the wiper carriage of the Strowger mechanism 300 to be driven step-by-step until the lower wiper set 30| .selects an idle outgoing trunk in the previously selected group, including the outgoing trunk 205, For reference purposes, it may be assumed that the particular outgoing trunk 205 in the group noted is selected, whereby the switch through relay R240 is operated in the manner previously explained. In the present case, upon operating the switch through relay R240 completes, at the contacts 241, a circuit, including the contacts 263, and the set of switch springs S305 for operating the repeater cutout relay R2|0. Upon operating, the repeater cutout relay R2 |0 interrupts, at the contacts 2|1, the previously traced circuit for energizing the upper winding of the line relay R255 in order to cause the latter relay to restore; and interrupts, at the contacts 2|9, the circuit for retaining operated the hold relay R260, whereby the latter relay is restored shortly thereafter. Also the repeater cut out relay R2|0 interrupts, at the contacts 2| and 2l4, the connections between the line conductors of the incoming trunk 20| and the windings 225 and 228 of the repeating unit 225; interrupts at the contacts 2|3 and 2|S, the connections between the windings 221 and 2 29 o;f the repeating unit 225 and the line wipers of the lower wiper set 30|; and completes, at the contacts 2|2 and 2|5, direct connections, including the contacts 24|, 242, 244, 245,292 and 294, between the line conductors of the incoming trunk 20| `and V,R230 andthe control wiper of 30| and completes, at connection, including the contacts 240 and 296, between the control conductor ofthe incoming trunk20| andthe Acontrol wiper of the lower wiper at the contacts i2 6.3, potential in the-.tollselector repeater 200 to the hold: conductor ,of the incoming trunk 20|; however, ,ground potential rswitch vtrain is retained Vofthe incoming trunk atedpthe switch through relay RMU-and the repeater cut out :through relay R240 retains completed, at the conand in response to a release Vline-conductors of the outgoing trunk-'205. Further the repeater cut out-relay R2|0 interrupts, lat the contacts 2 I8', the connectionbetweenf the winding -of` the supervisory relay the lower wiperset the contacts 2|3, a direct setg30 I.

`Upon restoring, the hold relay R260 interrupts, the path iorapplying ground in the preceding toll upon the hold conductor so as to retain operrelay R2 I0. The operated switch tactsZ 49, the pathk for applying ground potential to the hold wiper of the lower wiper set 30|,

" whereby the application of ground potential to the hold conductor of the outgoing trunk 205 retainsoperated the succeeding toll switch train. Further the hold relay R260 interrupts, at the contacts 20|, the circuitfor retaining operated the count relay R280, as well as Vthe multiple circuit for energizing-the right-hand winding of the answer relay R220. At this time, the toll selector repeater not only occupies its switched-through position but also its repeater cut-out positionl by virtue of the operated positions of the switch through relay R240. and the-repeater cut out relay 'R2|0. Accordingly, the line vconductors and the control conductor of the incoming trunk 20| are directly connected to the corresponding conductors of the outgoing trunk 205. Thus anyrdigits that are transmitted at this time over the control conductor of the incoming trunk-20| are forwarded directly via the control conductor of the outgoing conductor 205 to the succeedingswitch train in order to control operation thereof. Moreover any supervisory from the succeeding switch train via the line or control conductors of the outgoing trunk-205,:are returned directly over the corresponding conductors of .the incoming trunk 20 I and thepreceding toll switch trainlto the toll operator position, not shown. For example, should the succeeding toll switch train encounter an all-trunks-busy condition,A the all-trunks-busy signal is applied'to the control conductor of the outgoing trunk205 andis returned directly via the control conductor of the incoming trunk 20| and the preceding toll Iswitch train to the toll operator switchboard, not

shown, and is converted into an appropriate alltrunks-busy signal.

At the conclusion of the established connection that is lperformed over the preceding toll switch train, ground potential is removed from the hold conductor of the incoming trunk 20| eiecting the restoration of the switch through relay R240 and the repeater cut out'relay R2 I 0 in the toll selector repeater 200. 'Upon restoring, the switch through relay R240 Y effects operation of the release magnet M306, wherebythe Strowger mechanism 300 is released and returned to its normal rotary and vertical positions in the manner previously explained. In this case, the sets of switch springs S30I, S302, S305 and S306 are operated when the wiper carriage of the Strowger mechanism 300 is thus released. Specifically, the set of switchvsprings signals that'are returned operated. More specifically,

`operation of the switch supervisory relay R230.

S305 is Vopenedto:interrupt a1-further vpcliintfin the circuit for-operating thestep relay R285; and thecset of switch springs S306 is openedtointerrupt a further point in the circuitl for operating the repeater cut out relay R2|;0. Also upcnfrestoring, the repeater cut out relay l.R2 I0 iagain prepares, at the contacts 2| l, 2 I 3, 2 |4pand2 I 6,-the normal vinclusion of the repeating unit 225 be tween the line conductors of the incomingftrunk 20| and the line wipers of a lower wiper set 30|. At this time, the toll selector repeater 2001s completelyl releasedr and is avai-lablefor further use.-

Incident to the operation of the toll seiector repeater 200 to select an idle outgoing trunk in any one ofthe groups respectively including ,the outgoing trunks '202, 203, ,204,and205, it,may occur thatail of the loutgoing trunks inthe particular group are busy. Specifically following the two digits vl and `l all of the outgoing trunks in the group, including the outgoing trunk `202, may be tested as being busy; following the'two digits 1 and 2 all of the outgoing trunks in the giroup, including the outgoing trunk 203 may be tested as being busy; following the single digit2 all of the outgoing trunks in the group, including the outgoing trunk 20.4, may be tested as being blusy; and following .the single digit 3, all of the outgoing .trunks inthe group,` including the outgoing trunkf205, maybe tested as being busy. "In any case, operation of the Strowger mechanism l300 in the rotary direction continues until the wiper carriage thereof is driven eleven steps in the rotary direction away from its normal rotary position, whereby the sets of switch springs S303 and S304 are 'the setof switch open the right-hand positively to vprevent through relay R240. Also the set of switch springs S304 is operatedto close the left-hand contacts thereof so as to complete a circuit, including the contacts 263, for operating-the supervisory relay R230. Upon operating, the set oi switch springs vS503 is closed springs S304 is operated to contacts thereof lin order `to prep-are a connection between the busy conductor C222 and the upper winding of the line relay R250; which connection is completed, at the contacts 232, incident to operation of the At Vthis time, vground. potential is connected via the lower windingA of the line relay R2 50, the contact 233, the upper winding of the line relay R250 and the contacts 2|'I to the control conductor of the incoming trunk 20|; and |20 ground impulses Iper minute lare applied to the busy conductor C222, whereby ground potential is intermittently applied from the busy conductor C222 via the set of switch springs S303, the contacts 232, the upper winding of theV line relay R250 and the contacts 2 to the control conductor of the incoming trunk 20 Accordingly the lower high resistance winding Aof the line relay R250 Iis intermittently shortcircuited by the intermittent application of ground potential to the busy conductor C222 so that alternately low resistance ground potential and high resistance ground potential are returned via the upper winding of the line relay R250 and via the lower and upper windings of the line relay R250 to the control conductor of the incoming trunk 20| and thence by way of the preceding toll switch train to the'toll switchboard, not shown, serving as an all-trunksbusy signal in the manner previously explained.

Upon'receiving the busy supervision noted when the toll selector repeater 200 encounters the "all-trunks-busy condition, the operator at the toll switchboard performs a release control over the preceding toll switch train so` as to effect the restoration of the line relay R25@ and the supervisory relay R26-itl, whereby the toll selector repeater 2te is released in the manner previously explained.

In the foregoing description of the toll selector |09 and the toll selector repeater 2F36, it was explained that these automatic switches occupied intermediate positions in the associated toll switch trains. In fact, the toll selector repeater 209 and the toll selector it may occupy tandem intermediate positions in the same toll switch train. For example, in such an arrangement, the toll swithchboard, not shown, may have access to preceding toll switching apparatus, not shown, that has access to the toll selector repeater 25; the toll selector repeater 235i may have access to the toll selector itil; and the toll selector lee may have access to succeeding toll switching apparatus, not shown. For instance, the outgoing trunk 2M appearing before the lower wiper set te! in the Strowger mechanism 360 incorporated in the toll selector repeater 2lb? may in fact be the incoming trunk ill! extending to the toll selector itt; and the outgoing trunk |04 appearing before the lower wiper set lill of the Strowger mechanism lili? incorporated in the toll selector lili! may terminate a conventional toll connector. In this arrangement, it will be understood that the operator at the toll switchboard selectively operates the preceding toll switching apparatus via the control conductor thereof, effecting seizure of the incoming trunk 2t! extending to the toll selector repeater 7.99. The toll selector repeater 2M then receives the digit 2 via the control of the incoming` trunk Bilt and operates to select the outgoing trunk 2teincoming trunk le! extending to the toll selector Mill. The toll selector repeater Z then receives the digit 2 via the control conductor of the incoming trunk Ztl, which is repeated by the line relay R259, at the contacts 251, via the line conductors of the outgoing trunk 28d-incoming ..1

trunk lili to the line relay RIZ() in the toll selector I (it) in order to eiect operation of the toll selector ID to select the outgoing trunk ltd extending to the toll connector not shown. The toll selector repeater Zilli then receives two additional digits via the control conductor of the incoming trunk 2.5i, which are repeated via the line conductors of the toll selector It!! to the succeeding toll connector, not shown, in order to eiect operation thereof to select a subscriber -1 line having access thereto. In this case, in response to answering at the called subscriber substation the succeeding toll connector, not shown, operates to reverse battery over the line conductors of the outgoing trunk idd so as to eiiect operation of the answer relay R228 in the toll selector repeater 290 and the consequent return of answer supervision by the supervisory relay R23@ over the control conductor of the incoming trunk 295 and the preceding toll switching apparatus to the toll opera-tor position, not shown. In this arrangement, it will be understood that supervisory signals originating at the called subscriber substation are returned via the line conductors of the succeeding toll switch train to the answer relay R229 in the toll selector repeater 250 and are there converted into supervisory signals that are returned via the control conductor of the preceding toll switch train to the toll operator position. Specically as previously noted, the supervisory signals are converted by the supervisory relay R235 into high resistance and low resistance ground connections that areapplied to the control conductor or' the incoming trunk Edi and thencev returned in this form over the contro?. conductor of the preceding toll switch train to the toll operator switchboard, not shown.

In view of the foregoing, it rent that there has been provided automatic toll switching apparatus that embodies an improved and simpiied wiper switching and supervisory control arrangement.

While there has been described which is at present considered to be the preferred embodiment oi the invention, it will be understood that various modifications will be madetherein, and itis intended to cover in the appended claims al1 such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. In a telephone system, an automatic switch comprising a line, iirst and second wiper sets mounted for simultaneous select-ive primary and secondary movements, a iirst group of trunks accessible to said iirst wiper set, second and third groups or" trunks respectively accessible to said first and second wiper sets, means responsive to a first digit signal transmitted over said line for imparting corresponding selective primary movement to said wiper sets to cause said first wiper set to select said rst group of trunks or to cause said rst and second Wiper sets respectively to select said second and third groups of trunks, first means responsive to.

primary movement of said rst wiper set to select said first group of trunks for initiating secondary movement of said wiper sets so that said .first wiper set successively selects the individuai trunks in said rst group, a number of counting relays, means responsive to a second digit signal transmitted over said line for selectively operating said counting relays to register said second digit signal, means normally selecting said first wiper set, additional means responsive to operation of said counting relays to register a predetermined second digit signal for selecting said second wiper set, second means responsive jointly to primary movement of said first and second wiper sets respectively to` select said second and third groups of trunks and to operation oi at least one of said counting relays for initiating secondary movement of said. wiper sets so that said `iirst and second wiper sets successively select the individual trunks in said second and third groups respectively, a tester, and means controlled by said tester in response to the selection by said selected wiper set of an idle trunk in the selected group for arresting said secondary movement of said wiper sets and for completing a connection between said line and said selected wiper set.

2. In a telephone system, an automatic switch comprising a line, first and second wiper sets mounted for simultaneousselective primary and secondary movements, a first group of trunks accessible to said rst wiper set, second and third groups of trunks respectively accessible to said first and second wiper sets, means responsive to a. first digit signal transmitted over said line for imparting corresponding selective primary movement to said wiper sets to cause said Iirst wiper set to select said first group of trunks or to cause said rst and second wiper sets reaofzaais 'spectively to select said second and third groups of trunks, first means responsive to primary movement of said iirst wiper set to select said rst groupof trunks for initiating secondary movement of said wiper sets so that said iirst wiper set successively selects the individual trunks in said iirst group, iirst and second counting relays, means responsive to a second digit signal transmitted over said line for selectively operating said counting relays to register said second digit signal, said iirst counting relay being operated to register any value of said second digit signal and said second counting relay being operated to register a predetermined value of said second digit signa said second counting relay having a normal restored position selecting said iirst wiper set and an operated position selecting said second wiper set, second means respons-ive jointly to primary movement of said first and second wipersets respectively to select said second and third groups of trunks and to operation of said rst counting relay for initiating secondary movement of said wiper sets so that said Jfirst and second wiper sets successively select the individual trunks in said second and third groups respectively, a tester, and means controlled by said tester in response tothe selection bysaid selected wiper set of an idle trunk in the selected group .for arresting said secondary movement of said wiper sets and for completing a `connection between said line and said selected wiper set.

3. In a telephone system, an automatic switch comprising a line, iirst and second wiper sets mounted for simultaneous selective primary and secondary movements, first and second groups of trunks respectively accessible to said first and second wiper sets, Va line relay, iirst means including said line relay and responsive to a iirst digit signal transmitted over said line forimparting corresponding selective primary movement to said wiper sets to cause said iirst and second ,wiper sets respectively to select said iirst and second groups of trunks, first and second counting relays, second means including said line relay and responsive to a second digit signal transmitted .over said line for selectively operating said iirst and second counting relays so that said iirst counting relay is operated in the event said second digit signal has a value of one and so that said first and second counting relays are operated in the event said second digit signal has a value greater `than one, said second counting relay having a normal restored position selecting said first wiper set and an operated position selecting said second wiperset, means controlled following the transmission of said second digit signal over said line for initiating secondary movement of said wiper sets so that said iirst and second wiper sets successively select the individual .trunks in said first and second groups respectively, a tester, and `means controlled by said tester in response to the selection by said selected wiper set of an idle trunk in the selected group for arresting said secondary `movement of said Wiper sets and for completing a connection between said line and said selected wiper set.

4. In a telephone system, an automatic switch comprising a line, a voice signal repeating unit, iirst and second wiper sets mounted for simultaneous selective primary and secondary movements, a first group of .trunks access'ble to said first wiper set, second and third groups of trunks respectively accessible to said first and second wiper sets, means responsive to a digit signal f. said wiper sets so that 28 transmitted over said line for .imparting lco'rre sponding selective primary movement to said wiper sets to cause said iirst Wiper set to ,select said iirst group `of trunks or to cause said iirst and second wiper sets respectively to select said second and third groups of trunks, iirst means responsive to primary movement of said first wiper .set to select said iirst group of trunks for initiating secondary movement of said wiper sets so that said first wiper setsuccessively selects the individual trunks in said iirst group, ,a register, means for registering anotherdigit signal transmitted over said line in said register, meansnormally selecting said first Wiper set, additional means responsive to the registration -of a predetermined digit signal .in said .register for selecting said second wiper set, second means responsive jointly to primary movement of said iirst and second wiper sets respectively to select said vsecond and third groups of trunks and to the registration of a digit signal in said register for initiating secondary movement that said iirst and second wiper sets successively select the individual trunks in said second and third groups respectively, a tester, ,means controlledby said tester in response to the selection by said selected wiper set of an idle trunk inthe selected group for arresting said secondary movement of said wiper sets and for completing Aa connection between said .line and vsaid selected wiper set, and additional means selectively controlled in accordance with the `primary movement of said wiper sets for respectively including and excluding said repeating unit in said connection between said line and said selected wiper set.

5. In a telephone system, an automatic switch comprising a line, a Yvoice signal repeating unit, irst and second wiper sets mounted for simultaneous selective primary and secondary movements, a iirst group of trunks accessible to said first wiper set, second and third groups of trunks respectively accessible to said first and second wiper sets, means responsive to a digit signal transmitted over said line for imparting corresponding selective primary movement to said wiper sets :to cause said iirst wiper set to select said iirst group of trunks or to cause said iirst and second wiper sets respectively to select said second and third groups of trunks, a cut out relay, first means responsive to primary movement of said iirst wiper set to select said first group of trunks for conditioning said cut out relay and for initiating secondary movement of said first wiper set successively selects the individual trunks in said iirst group, a register, means for registering another digit signal transmitted over Vsaid line in said register, means normally selecting said nrst wiper set, additional means responsive to the registration of a predetermined digit signal in said register ,for selecting said second wiper set, second means responsive jointly to primary movement of said rst and second wiper sets respectively to select said second and third groups of trunks and to the registration of a digit signal in said register for initiating secondary movement of said wiper sets so that said first and second wiper sets successively select the individual trunks in said second and third groups respectively, a tester, means controlled by said tester in response to the selection by said selected wiper set of an idle trunk inthe selected group for arresting said secondary movement of said Wiper sets and for operating said cut out relay of said wiper sets fso,

229 in the event it is conditioned and for completing a connection between said line and said selected wiper set, said connection normally including said repeating unit, and means responsive to operation of said cut out relay for cutting said repeating unit out of said connection.

6. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a Wiper set including a pair of line Wipers and a control wiper and a hold wiper, an outgoing trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay, means controllable over the control conductor of said incoming trunk for selectively operating said line relay, a source of hold potential, means responsive to initial operation of said line relay for connecting said source of hold potential to the hold conductor of said incoming trunk, means responsive to subsequent restoration and reoperation of said line relay for operating said wiper set to select said outgoing trunk, a first relay, a second relay, means responsive to said last-mentioned operation of said wiper set for connecting said hold potential to the hold wiper of said wiper set and for connecting said first relay to the line Wipers of said wiper set and for connecting said second relay to the control Wiper of said wiper set and for completing a connection between the line conductors of said incoming trunk and said line wipers, means responsive to a supervisory control on the line conductors of said outgoing trunk for operating said rst relay, means responsive to operation of said iirst relay for operating said second relay, additional means responsive to a supervisory control on the control conductor of said outgoing trunk for operating said second relay, and means responsive to operation of said second relay for returning a supervisory control over the control conductor of said incoming trunk.

7. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay provided with first and second windings that are respectively of low resistance and high resistance with respect to each other, a source of first potential, a iirst connection from said source of first potential via said rst winding to said control conductor, a second connection from said source of first potential via said second and rst windings in series to said control conductor, a supervisory relay having a restored position completing said iirst connection and interrupting said second connection and having an operated position completing said second connection and interrupting said rst connection, a source of second potential adapted to be selectively connected to said control conductor in order selectively to energize said first winding or said first and second windings depending upon the completion of said first or second connections respectively, said line relay being operated when either said first winding is energized or said rst and second windings are energized, a source of hold potential, means responsive to initial operation of said line relay in response to initial connection of said source of second potential to said control conductor for connecting said source of hold potential to said hold conductor, a wiper set, a line accessible to said wiper set, means responsive to operation and restoration of said line relay in response to one or more impuless of said source of second potential connected to said controlconductor for operating said Wiper set to select sa1d line, means responsive to selection of said line by said wiper set for completing a connection between said line conductors and said wiper set, and means responsive to an answer control on said line for operating said supervisory relay and responsive to a disconnect control on said line for restoring said supervisory relay.

8. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay provided with rst and second windings that are respectively or" low resistance and high resistance with respect to each other, a source of rst potential, a rst connection from said source of first potential via said first winding to said control conductor, a second connection from said source of first potential via said second and rst windings in series to said control conductor, a supervisory relayhaving a rst position completing said nrst connection and interrupting said second connection and having a second position completing said second connection and interrupting said rst connection, a source of second potential adapted to be selectively connected to said control conductor in order selectively to energize said first Winding or said rst and second windings depending upon the completion of said first or second connections respectively, said line relay being operated when either said first winding is energized or said first and second windings are energized, a source of hold potential, means responsive to initial operation of said line relay in response to initial connection of said source or second potential to said control conductor for connecting said source or" hold potential to said hold conductor, a wiper set, a line accessible to said wiper set, means responsive to operation and restoration of said line relay in response to one or more impulses of said source of second potential connected to said control conductor for operating said wiper set to select said line, means responsive to selection of said line by saiii wiper set for completing a connection between said line conductors and said wiper set, and means responsive to supervisory controls on said line for selectively operating said supervisory relay between its iirst and second positions.

9. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay provided with iirst and second windings that are respectively of low resistance and high resistance with respect to each other, a source of rst potential, a first con-Y nection from said source of first potential via. said first Winding' to said control conductor, a second connection from said source of i'irst potential vla said second and first windings `in series to said control conductor, a supervisory7 reiay having a first position completing said .irst connection and interrupting said second connection andhaving a second position completing said second connection and interrupting said nrst connection, a source of second potential adapted to be selectively connected to said control conductor in. order selectively to energize said Winding or said iirst and second windings depending upon the completion of said first or second connections respectively, said line relay being operated when either said Erst winding is energized or said rst and second windings are energized, a source ofj hold potential, means responsive to initial opere` 3i ationfof said line relay inresponse yto :initial connection ofsaid source of second potential to said control conductor .for connecting said source of hold, potential to said .hold conductona wiper set including .a .pair of line Iwipers .and a control wiper and a hold wiper, an outgoing trunk in cluding a pair of line conductors and a control conductor and a holdconductor, means vresponsive to operationand restoration of .said line relay in response to one or moreimpulses of said source of second potential connected tosaid control conductor foi` operating said wiper set to select said outgoing trunk, and means responsive to selection .of said outgoing trunk for connecting said hold potential to the hold wiper of said wiper set and for completing aconnection between theline conductors of said incoming trunk and said line wipers and for connecting said supervisory relay to said control wiper, said supervisory relay being selectively operative between its first and second positions in response to supervisorysignals on the control conductor of said outgoing trunk.

l0. In a telephone system, an automatic switch comprising an incoming trunk including d pair of line conductors anda control conductor and a hold conductor, a line relay provided with first and second windings that arerespectively of low resistance and high resistance with respect to each-other, a source of'first potential, arfirst connection lfrom said source of first potential via said rst winding to said lcontrol conductor, a second connection-from said source of rst potential via said second and first windings in series to said control conductor, a supervisory relay having a restored position completing said rst connection and interrupting said second connection and having an operated position completing said second connection and interrupting said rst connection, a source of second potential adapted to be selectively connected to said control conductor in order` selectively to energize said first winding or said first and second windings depending upon the completion of said nrst or second connections respectively, said line relay being operated when either said first winding is energized or said first and second windings are energized, a source of hold potential, means responsive to initial operation of said line relay in response to initial connection of said source of second potential to said control conductor for connecting said source of hold potential to said hold conductor, a wiper set, a group of lines accessible to said wiper set, means responsive to operation and restoration or said line relay in response to one or more impulses of said source ofr second potential connected to said control conductor for operating said wiper set to select said group of lines, means for initiating operation of said wiper set to select an idle one of the lines in said group, means responsive to selection by said wiper set of an idle line in said group for arresting said last-mentioned operation thereof and for completing a connection between said line conductors and said wiper set, means responsive to an answer control on a line in said groups selected by said wiper set for operating said supervisory relay, and means including a busy device operated in response to a busy condition of all of the lines in said group for alternately completing and interrupting said iirst and secondconnections.

l1. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay provided with first andzsecond windings that are respectively of low resistance and high resistance with respect to each other, a source of rst potential, arstconnection from said source of iirst potential'via said first winding vto said control conductona second connection fromsaid source of rst potential via said secondand first windings in series to said control conductor, a supervisory relay having a rstposition completing said first connectionand interrupting said second connection and having a second position completing said second connection and interrupting .said first connection, a source of second potential adapted to be selectively connected to said control conductor yin order selectively to energizesaid rst wndingor said first and second windings depending upon the completion of said first orsecond connections respectively, said line relay being operated when either said iirst winding isenergized or said rst and second windings are energized, a source of hold potential, means responsiveto initial operation of said line relay in response to initial connection of said source of second potential to said control conductor for connecting said source of holdpotentialto said hold-conductor, a wiper set, aline accessible to said wiper set, means responsive to operation and restoration of said line ,relay in response to one or more impulsesiof said source of second potential connected to said control conductor vfor operating said wiper setto select said line, means responsive to selection of said line by said wiper set for completing acon-l nection between said line conductorsk and said wiper set, means responsive to supervisory controis on saldrline for selectively operating said supervisory relay between its first and second positions, and means including a busy device operated in response to a busy operation of said wiper set i'or intermittently completing and interrupting said first and second connections.

12. ln a telephone system, an automatic switch comprisingan incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay provided withirst and second windings-that are respectively of low resistance and high resistance with respect t0 each other, a source of first potential, a first connection from said source of first potential viasaid rst winding to said control conductor,.a second connection from said source of rst potential via said second and first windings in series to `said control conductor, a supervisory relay having a first position completing said first connection and interrupting said second connection and having a second position completing said second connection and interrupting said first connection, a source of second potential adaptedto be selec-V tively connected to said control conductor yin order selectively to energize said iirst winding or said first and second windings depending upon the comple-tion of said iirst or second connectionsrespectively, said line relay being operated when either said first winding is energized or said viirst and second windings-are energized, a source of hold potential, .means responsive to initial opera.- tion of said line relay in responseto initial connection ofsaid source of second potential-to said control conductor for connecting said source of hold potential to said hold conductor, a wiper set, a line accessible to said wiper set, means responsive to operation and restoration of said line relay in response to one or more impulses ofrsaid source of second potential connected to said control conductor for operating said wiper set toselect said line, means responsive -to selection ofsaid lineby said Wiper-set for completing a connection Ybe@ tween said line conductors and said wiper set, means responsive to supervisory controls on said line for selectively operating said supervisory relay between its first and second positions, busy contacts operated in response to a busy operation of said wiper set, and a busy conductor having said source of iirst potential intermittently connected thereto, operation of said busy contacts connecting said busy conductor via said first winding to said control conductor.

13. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a wiper set including a pair of line wipers and a hold wiper, an outgoing trunk including a pair of line conductors and a hold conductor, a line relay, means controllable over the control conductor of said incoming trunk for selectively operating said line relay, a source of hold potential, means responsive to initial operation of said line relay for connecting said source of hold potential to the hold conductor of said incoming trunk, means responsive to subsequent restoration and reoperation of said line relay for operating said wiper set to select said outgoing trunk, an answer relay, means responsive to said last-mentioned operation of said Wiper set for connecting said hold potential to the hold wiper of said wiper set and for connecting said answer relay to the line wipers of said wiper set and for completing a connection between the line conductors of said incoming trunk and said line wipers, means responsive to further restoration and reoperation of said line relay for repeating corresponding impulses over` the line wipers of said wiper set and consequently over the line conductors of said outgoing trunk, means responsive to an answer control on the line conductors of said outgoing trunk for operating said answer relay, and means responsive to operation of said answer relay for returning an answer signal over the control conductor of said incoming trunk.

14. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, Aa wiper set including a pair of line wipers and a control wiper and a hold wiper, an outgoing trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay, means controllable over the control conductor of said incoming trunk for selectively operating said line relay, a source of hold potential, means responsive to initial operation of said line relay for connecting said source of hold potential to the hold conductor of saidincoming trunk, means responsive to subsequent restoration and reoperation of said line relay for operating said wiper set to select said outgoing trunk, a rst relay, a second relay, means responsive to said last-mentioned operation of said wiper set for connecting said hold potential to the hold wiper of said wiper set and for connecting said iirst relay to the line wipers of said wiper set and for connecting said second relay to the control Wiper of said wiper set and for completing a connection between the line conductors of said incoming trunk and said line wipers, means responsive to further restoration and reoperation of said line relay for repeating corresponding impulses over the line wipers of said Wiper set and consequently over the line conductors of said outgoing trunk, means responsive to a supervisory control on the line conductors of said outgoing trunk for operating said first relay, means responsive to operation of said iirst relay for operating said second relay, additional means responsive to a supervisory control on the control conductor of said outgoing trunk for operating said second relay, and means responsive to operation of said second relay for returning a supervisory control over the control conductor of said incoming trunk.

15. In a telephone system, an automatic switch comprising an incoming trunk including a pair of line conductors and a control conductor and a hold conductor, a Wiper set including a pair of line wipers and a control and a hold wiper, a rst outgoing trunk including a pair oli line conductors and a control conductor and a hold conductor, a second outgoing trunk including a pair of line conductors and a control conductor and a hold conductor, a line relay normally connected to the control conductor of said incoming trunk, said line relay being selectively operable over the control conductor of said incoming trunk when it is connected thereto, a source of hold potential, means responsive to initial operation of said line relay for connecting said source of hold potential to the hold conductor of said incoming trunk, means responsive to subsequent restoration and reoperation of said line relay for selectively operating said wiper set to select either said first outgoing trunk or said second outgoing trunk, a voice signal repeating unit including coupled primary and secondary windings, a rst relay, a second relay, means responsive to operation of said wiper set to select said first outgoing trunk for connecting said hold potential to the hold wiper of said wiper set and for connecting the line conductors of said incoming trunk to said primary winding and for connecting said secondary winding and said first relay in series to the line wipers of said wiper set and for connecting said second relay to the control wiper of said wiper set, means responsive to a supervisory control on the line conductors of said first outgoing trunk for operating said iirst relay, means responsive to operation of said lirst relay for operating said second relay, additional means responsive to a supervisory control on the control conductor of said first outgoing trunk for operating said second relay, means responsive to operation of said second relay for returning a supervisory control over the control conductor of said incoming trunk, and means responsive to operation of said wiper set to select said second outgoing trunk for connecting said hold potential to the hold wiper of said wiper set and for disconnecting said line relay from the control conductor of said incoming trunk and for connecting the line conductors and the control conductor of said incoming trunk to the respective line wipers and control wiper of said wiper set.

PIER BAKKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,474,008 Stokely Nov. 13, 1923 1,546,113 Albert July 14, 1925 1,577,083 Sperry Mar. 16, 1926 1,914,357 Brooks June 20, 1933 2,052,051 Lomax Aug. 25, 1936 2,504,708 Long Apr. 18, 1950 

